Lung Cancer
PKGhatak,MD
Lung
cancer is a fatal illness. Incidence and deaths from lung cancer are steadily
increasing in developing parts of the world, as they did in the West
after the end of WWII and the incidence of new cases of lung
cancer is directly related to cigarette smoking and industrialization
with the degradation of the environment.
Basically, there are two classes of lung cancers.
Small cell lung cancer.
Non-small
cell lung cancer. (NSCLC)
The above
classification is based not only on the pathological features of the
cancer cells but also applies to symptomatically, tumor spread,
response to therapy and prognosis.
Susceptible
population.
Adults
with a long history of cigarette smoking, working in places where air or soil or water is contaminated with radioactive elements, those who are carriers of BRACA 2
gene, survivors of leukemia and other malignancy, and those who received chest radiation, people receiving
immunosuppression therapy following organ transplants or having autoimmune
diseases are susceptible for lung cancer. Incidences
are also higher in patients with a certain type of pulmonary fibrosis
and scar tissue in the lung. Exposure to radon gas and asbestos are
recognized risk factor. Exposure to heavy metals, specially arsenic, is
carcinogenic. A higher incidence in Sarcoidosis is a risk factor.
Symptoms at the time of Presentation.
Patients
may not have any symptoms and cancer is incidentally detected when a chest
X-ray was taken for other reasons. In the early stages, in symptomatic patients, an unproductive cough is
usual. Some patients develop asthma for the first time in midlife. Some
patients seek help when they coughed up bright red blood. Other symptoms are as follows. - Feeling
vague symptoms of not feeling well, unintended weight loss, hoarseness
of voice, lump in the neck area, weakness of large muscle groups of hips
making getting up from bed or chair difficult and then the weakness of
shoulder muscle limits patients' ability to raise hands overhead -
Lambert-Eaton syndrome. Unexplained neuritis of one or more peripheral nerves in different parts of the body. Pain over spinal bones or ribs. Some have convulsions as first the presenting symptoms. Clubbing of fingers, pretibial edema and tenderness
over lower tibial bones. Deep vein thrombosis, neuromusculopathy,
peripheral neuritis and dermatomyositis are also presenting symptoms.
Special features of Small Cell Cancer.
Small cell carcinoma is only 15 % of the total lung cancer population. Under
the microscope, the cancer cells resemble carcinoid cells. There
is a very strong correlation with cigarette smoking. Patients are
often male and in middle aged group. The common symptom which brings them
to doctors is chest pain which is often mistaken for heart attacks
or angina. Initial routine chest x-rays often appear normal. Either
by CT scan of the chest or very expert radiologists can detect a faint
outline of a tumor on chest x-rays, located on the upper lobe of the lung and in the hilar region.
Early
hilar lymph node enlargement produces pressure symptoms on the local
structures. As more tissues are infiltrated by tumor cells, and more symptoms develop this is called Thoracic Inlet syndrome, the symptoms of Thoracic Inlet syndromes are A. 1. Inferior cervical ganglion and paravertebral sympathetic chain
infiltration by cancer cells produce a dropping of the upper eyelid with 2. a small constricted pupil and 3. loss of sweating on the involved side of the forehead. This symptom complex is called - Horner syndrome.
B. Pain in the arm and forearm in the
distribution of brachial plexus nerves.
C. Superior vena cava obstruction
producing edema of head and neck, bluish discoloration of face,
distended conjunctival vessels.
D. Infiltration may include the phrenic
nerve producing paralyzed hemidiaphragm.
E. Infiltration of
apical pleura may produce pruritic chest pain and pleural effusion.
Paraneoplastic
syndrome. The small cell cancer cells and rarely alveolar cell cancer, at times, secrete hormones like polypeptides and produce a variety of
symptoms. A few of them are mentioned here.
Cushing's
syndrome is due to excess ACTH secretion. Hyperparathyroidism produces
high serum calcium and symptoms related to it. TSH like hormone
secretion leads to thyrotoxicosis. Insulin like hormone
produces severe hypoglycemia. Melanin like peptide producing
Acanthosis nigricans - dark pigmentation of skin in intertriginous areas and the flexural surface of limbs. Severe hyponatremia due to inappropriate
antidiuretic hormone production (ADH) causes excess free water reabsorption
in renal tubules.
Tumor
cell behavior.
Tumor
cells spread early and often by the bloodstream to the brain and bones.
Biopsy.
Fine
needle aspiration biopsy under ultrasound guidance yields good
results. Often bone marrow biopsy is required for diagnosis and staging.
The cancer cells are small and rounded with a thin margin of peripheral cytoplasm, and coarse chromatin without a nucleolus. The cytoplasm contains neurosecretory
granules in 90 % of cases. No immunological staining is possible.
Treatment.
In the localized early stage of the disease, chemotherapy containing Cisplatin or Carboplatin and
Etoposide followed by cranial radiation is recommended. In widespread
diseases, a combination of chemotherapy and chest radiation therapy is
followed by cranial radiation is done. No immunotherapy drug has any
role in the treatment of small cell cancer.
Prognosis.
The 2-year survival rate in late presentation is disappointing, only 2 to 5 %, and 20 to 40 % in early cases.
Non-Small Cells Lung Carcinoma (NSCLC).
This group contains Adenocarcinoma, Squamous cell carcinoma, Large cell carcinoma, alveolar cell carcinoma and others.
Special features of NSCLC.
85 % of all carcinoma of the lung fall into this group, and adenocarcinoma leads this group.
Nonsmokers and smokers, unfortunately, are both susceptible to Non-Small
Cell cancer of the lung. Malignant transformation of squamous dysplasia, a
common occurrence in smokers, into squamous carcinoma is a usual occurrence. Adenocarcinoma may
develop from preexisting scars. Delayed clearing of pneumonia, bloody
sputum, or associated pleural effusion may be the presenting symptoms.
High serum calcium is often seen in squamous cell carcinomas from
osteolytic bone metastasis. Seizures from single brain metastasis are
seen in adenocarcinomas. Early metastasis via blood is common in
adenocarcinomas. Hypertrophic Pulmonary Osteodystrophy (HPO) is often seen. The HPO is characterized by burning pain and red discoloration of the skin over the tibia
and knees, edema, clubbing of fingers, and tender wrists and fingers due to
subperiosteal new bone formation. Squamous cell carcinomas are usually centrally located and produce
hemoptysis. Adenocarcinomas are usually located at peripherally and arise
from mucus glands and or from the epithelial cells of terminal
bronchioles.
Alveolar carcinomas are included in the adenocarcinoma group but
it has some distinct features - generally have multiple sites of origin,
patients have vague symptoms that can go on for a significant time period; patients often develop
neurological symptoms or psychological problems. The diagnosis is often delayed because
sputum examinations generally are free of cancer cells and the tumors
are not accessible to bronchoscopic view. A lung biopsy is required for
diagnosis.
Large cell cancers are rapid growers, maybe central or
peripheral in location.
Diagnosis.
Bronchoscopy
and bronchoscopic biopsy of the lesion are preferred. If the tumor mass is
not accessible by bronchoscopy, then ultrasound guided fine needle
aspiration biopsy is recommended. In cases where hilar lymph nodes are present, suprasternal mediastinoscopy is preferred for biopsy and staging.
Immunohistochemical staining of biopsy helps the identification of cell types and subtypes.
The
initial diagnosis is followed by the detection of mutation genes or genes
which have great importance in the treatment with immunotherapy and the use of immunotherapy
improves survival.
Treatment.
Surgery
is the preferred treatment modality in all cases of NSCLC wherever
possible. Surgery is followed by chest radiation therapy in localized
disease without lymph node involvement.
In the case of lymph node involvement or evidence of distant metastasis
Chemotherapy and radiation therapy are added after surgery. Chemotherapy agents are Platin based, most institutions follow their own protocols but all protocols include platins.
Prognosis of NSCLC and Immunotherapy.
The
patients live 2 to 5 years following surgery and when combined
with chemotherapy and /or radiation patients may live an additional 10 to 24
months.
Immunotherapy has added a new line of cancer therapy with good to
excellent results in patients who were dimmed too far advanced or did
not respond adequately to surgery and chemo-radiation therapy.
Immunotherapy:
Epidermal Growth Factor Receptor blockers, Tyrosine Kinase blockers,
PD1, PD-L1 antibodies, CTLA 4 receptor blocking antibodies are
available. These are briefly mentioned here.
Epidermal Growth Factor (EGF) – EGF is a protein first detected in the submandibular salivary and
parotid glands. It promotes tissue repair, cell growth, and wound
healing of the mouth, stomach and intestine. Subsequently, a group of
proteins, similar in structure and functions was also found in many
other tissues including immune cells. EGF binds with its
receptors on the cell surface and then induces Tyrosine kinase - a key
to the cell division, growth, and development of normal tissue. The gene
that controls EGFR (epidermal growth factor receptor) can mutate and
this leads to greatly increased receptors on the cell surface that
result in excess cell growth. This is particularly seen in some
cases of non-small cell cancer of the lung. Antibodies to EGFR are now
available for treatment. The antibodies block EGFR receptors present on the cancer cell surface and prevent
binding with ERGF and thereby preventing the progression of cancer.
Program Cell Death Protein 1(PD 1) is
another cell growth regulating protein. This is a surface protein
abundant on T cells surface. When it binds with its receptors, it down
regulates immune response to foreign agents or cancer cells.
Another transmembrane protein is Programmed death Ligand 1 (PD-L1).
When PD-L1 binds with PD1 receptors, it performs dual functions. 1. reduces antigen-specific T cells
in lymph nodes. 2. decreases apoptosis (programmed cell death) of normal T cells. Thereby
reduces immunologic reactions. Non-small cell cancer of the lung has a rich supply of PD-L1
receptors and thereby evades Killer T cells and cancer progresses
unchecked.
CTLA4 (cytotoxic T lymphocyte protein
4) is also called CD152, is a protein receptor, when binds with
CD80 and CD86 it down regulates immune reactions and when binds with
CD 28 it up regulates immune responses. Blocking antibody is available
against CTLA4 and when combined with PD1 or PD-L1 antibody therapy the
results are much superior to those used alone.
Unfortunately, immunotherapy also has adverse side effects. The immune
cells can attack the skin, lungs, liver, nervous system, heart and kidneys
and other organs. In such an instance, the immunotherapy has to be
terminated.
Prognosis of non-small cell Lung Cancer.
The prognosis of lung cancer is not good. The 5-year survival is 18 %. Immunotherapy has greatly improved
survival time in those who have the appropriate mutation of gene/ genes.
In
the 13 August 2020 issue of the New England Journal of Medicine, an
article on lung cancer clearly shows the declining incidence of lung cancer
since 2001 and more impressive is the decline in the death rates. In the case
of NSCLC, these results are due to the combined effects of decreased cigarette smoking in
the USA population and the availability of immunotherapy drugs. The rate of
decline of death rates nearly doubled from 2013 to 2016 when compared
with the decline rate of new cases of lung cancers; conforming to the
effectiveness of immunotherapy. In the case of small cell carcinoma, the
decline in mortality is entirely due to a decrease in cigarette smoking,
since immunotherapy for small cell cancer is not available.
In recent years, far advanced lung cancer cases many centers are treating patients with Chemotherapy plus Immunotherapy without looking into PD1 or other gene mutations. This practice is now extended to Small Cell cancer patients also. According to them, this combination showed improved survival time. However, it should be noted it is a palliative treatment.
If
nothing else can convenience you, this study should. Do not doubt the benefits of giving up cigarette smoking. If you want to live a
long life, this gives you one more chance. As an ad for satellite TV says " so,
what are you waiting for"
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